A steam turbine is used to drive a machine or the like. The steam turbine includes a turbine main body having a rotor which is rotatably supported. The rotor is rotationally driven by supplying steam serving as a working fluid to the turbine main body. Steam supplied to the turbine main body or steam extracted from the turbine main body flows through a steam flow path of the steam turbine. A governing valve is provided in the steam flow path. A flow rate of steam supplied to the turbine main body can be regulated by regulating an opening degree of the governing valve.
The governing valve is driven by a governing valve drive mechanism. In general, a hydraulic servo mechanism is used as the governing valve drive mechanism.
Meanwhile, for example, in order to achieve space saving or the like, PTL 1 suggests a governing valve drive mechanism which includes an electric motor, and a conversion mechanism such as a ball screw which converts a rotational motion of the electric motor into a linear motion of a governing valve.